1. Field of the Invention
This invention relates to an injection molding nozzle to be used for injection molding of resin or molten metal.
2. Related Background Art
Known nozzles, nozzle main bodies and valve pins to be used for injection molding are typically made of metal such as tool steel and hence cannot be used with glass fiber, carbon fiber, resin containing a filler material and molten metal.
Known injection molding nozzles made of metal are accompanied by the following problems.
(1) The metal has a low hardness and is chemically unstable so that the gas or the fluid forced to penetrate into the gap between the injection molding nozzle and the valve pin by the temperature and the pressure of the material to be injected can seize the valve pin. PA0 (2) The pliability of the metal can give rise to a collapse on the part of the valve pin and a certain degree of deviation in the coaxiality between the valve pin and the gate. PA0 (3) The metal shows a large coefficient of thermal expansion to make it difficult to maintain a high degree of machining accuracy during the manufacturing process. PA0 (4) The large coefficient of thermal expansion and the easy cuttability of the metal make it difficult to enhance the surface smoothness and the surface planeness.